Following the acquisition of AuthenTec in July 2012, Apple introduced
the fingerprint reading feature with the iPhone 5S. It is currently the
only device of Apple incorporating such a feature, called Touch ID, but
other devices should follow later in 2014.

The fingerprint sensor of the iPhone 5S is included in the home button.
It features a square shape, distinguishing it from the traditional
rectangular swipe sensors. This square shape allows it to scan the
fingerprint just by pushing the button. The sensor features a resolution
of 7,744 pixels with a pixel density of 500ppi. It uses a capacitive
touch technology to take an image of the fingerprint from the
subepidermal layers of the skin.

The sensor is 170µm thick and is directly attached to a protective
window, therefore cavities are etched on the edges for the wire bonding
connections.

The protective window is made from sapphire crystal and is extracted by
laser cutting of Double Side Polished (DSP) sapphire wafers. The
sapphire window is then coated with two different materials.